Questions tagged [optics]

Optics is the study of light, and its interaction with matter. It includes topics such as imaging systems, fiber optics, lasers, quantum optics, and more.

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Interference questions

non reflecting surfaces are made by coating very thin films of transparent materials . find the maximum thickness of such coating is u=5/4 and l= 5.5*10-5 cm. What does it mean by maximum thickness?
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Polarisation circularly polarised light

How to distinguish between circularly polarized light and unpolarised light when passed through rotating nicole prism?
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19 views

How to design material to avoid (light) reflections?

I wondered how a material (maybe for example a glass window) must be made to provide none or very few reflections. And while I think about it I don't really know which interaction is behind reflection....
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Physics behind rays of light in the photographs taken in the darkness

What is the physics behind these rays of light visible in the photographs of objects that emit light? What justifies their shape and amount of rays? Very well known effect in a sense, but I did not ...
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38 views

3D reflection of a ray on a cylindrical mirror

I am trying to calculate the reflection of a ray on a cylindrical mirror in a three-dimensional space. To achieve this, can I apply the laws of reflection separately in xy and xz planes (as in the ...
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1answer
55 views

Why does a rainbow only form with a 42° angle? [duplicate]

Why do rainbows only form with a 42° angle? Is there something special about this angle?
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80 views

What would a lens-less world look like to us? [on hold]

The images we perceive through our eyes are formed by focusing the incoming light with the eye's cornea and lens. The information is "captured" by the retina and then transmitted to our brains through ...
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Rainbow angle wider than 90 degrees?

A rainbow is formed at the boundary between two materials that bend light differently, such as water and air. Using the laws of optics, you can find a formula for the angular size of a rainbow in ...
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52 views

Confusion regarding the reasoning for why constructive interference is hard to determine in Single-Slit Experiment

We know that the location of dark spots in Single-Slit experiment is given by the following equation: $$m\lambda = d\sin\theta$$ Where $m = 1,2...$ $d$ is the width of the slit and $\theta$ is the ...
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44 views

Detection of an optical noise with a photodetector, noise-equivalent power (NEP)

I am trying to find the minimum power that can be detected by a photodetector for which I know its noise-equivalent power (NEP). The standard formulas are: $$\mathrm{SNR} = \frac{\langle i_s^2(t)\...
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110 views
+100

Ray Tracing and Rotations

I would like to be able to write the matrix operations to be able to define the first arm of the picture below. How can I do that? I have learned beam physics, have read Siegman's Lasers, if that ...
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Photographic objective for telecentric lens

I am working on designing an image space telecentric lens assembly. I was having a hard time deciding which photographic objective type is best suited for such a lens. Most of the designs that I came ...
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Can we study the effects of Quantum reflection on heavy atoms?

From what I've looked at, it feels like QR has only been studied on light atoms like He, Ne, Na, H, etc. But can we study this effect on heavy atoms like Rb-87. If not, is it because of the ...
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Can a mirage cause the hull of a ship to disappear before the sails?

"Mirage-effect" helps researchers hide objects The article linked above describes how the effect can be used to make an object disappear. I am looking into flat earther beliefs and stumbled upon ...
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PN junction under forward or reverse bias, there is a current continuity through the depletion region

Will there be some generations by thermal happened in the depletion region?
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1answer
28 views

How can the loss of light irradiance due to both attenuation and the inverse square law be modelled?

When considering the effect of depth on just light attenuation (is within an aqueous solution), the Beer-Lambert law is used. From what I've found, the law is derived by determining the fractional ...
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Focusing a Gaussian beam into a nonlinear crystal

Boyd analyzes in his book (Boyd's book), section 2.10.3, the case of harmonic generation using a focused Gaussian beam and he mentions that an analytic solution can be evaluated for certain special ...
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45 views

How to explain this thumb experiment?

Close your thumb to your eyes and align your eyes, thumb and moon. Then focus your eyes on your thumb and watch the moon behind your thumb. You will find that the moon becomes small! Remove your thumb ...
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Why aren't rainbows blurred-out into nothing after they are produced?

I understand how a prism works and how a single raindrop can scatter white light into a rainbow, but it seems to me that in normal atmospheric conditions, we should not be able to see rainbows. When ...
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“There aren’t seven colors in the rainbow” is this claim appropriate? [closed]

This post says There aren’t seven colors in the rainbow, or any other specific number; Newton described seven colors in large part because of the supposed “...
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If you can see the sun's reflection on the windshield of a car, why probably can't the driver see you?

This comment avers, on What knowledge might save your life one day? : AskReddit If you're a pedestrian and crossing a street, if you can see the sun[']s reflection on the windshield of a car, there'...
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2answers
35 views

Do mirages really occur due to total internal reflection?

Mirages occur in areas such as deserts due to difference in the refractive indices of layers of air. As the light ray travels from denser to rarer layers of air, slowly bending, it approaches the ...
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Why does focus change when object is behind a glass slide?

I have an object that I am observing and focusing on, on a microscope slide. Half of the object is naked and half is covered with another microscope slide (not a coverslip). Why do I have, in order to ...
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1answer
17 views

Do dieletric mirrors and other reflective surfaces have a maximum intensity to which the absoprtion coefficient increases?

That is, if you shine a laser at a dielectric mirror so that the intensity(photons/seconds*cm^2)becomes sufficiently large, the scattering of the photons off the electrons in the surface atoms becomes ...
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Lorentz Oscillator and dielectric function: Incorrect formulation in textbook?

According to what I was taught in school the relative dielectric function for a Lorentz-Oscillator can be formulated as: $ \epsilon(\omega)=\epsilon_\infty+\frac{\omega_p^2}{\omega_0^2-\omega^2+j\...
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19 views

Photometry - Photopic and Scotopic vision

I would like to measure the eye sensitivity to a blue LED when a person is placed in a dark room. I need to convert the luminous flux (lumen) to optical power (W). Can someone tell me if I should use ...
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Problem related to combination of lens & equivalent focal length and lens maker's formula [closed]

in between two equiconvex lens( made of glass) of focal length of 20cm there is a layer of water which also acts as a convex lens.The whole figure is surrounded by air. Find out it's equivalent focal ...
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How to identify properties of a concave diffraction grating

As a little side project I want to build a spectrometer. The main components are an entrance slit, a concave diffraction grating and a CCD sensor (also the electronics). I bought a used diffraction ...
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1answer
21 views

Overall power/focal length of an eye and corrective lens system

Hey. I got this question wrong and I don’t get the explanation. I know that to fix myopia you need a concave lens to diverge the light rays so that the eye lens converges them further back on the ...
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2answers
17 views

Is there a way to precisely measure or infer the color of a material from a distance (~2m)?

I've recently started working on a graphics/SLAM project. I've encountered a problem that requires the measurement or inference of the color / spectral reflectance (and ideally albedo) of points on ...
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Why exactly are the diffraction and elastic coherent scattering of light different things?

In solving diffraction problems, as far as I know, physicists treat the distribution of optical properties of the obstacle with wave equation, applying different simplifications (such as Fraunhofer ...
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1answer
46 views

How do I explain the below phenomenon I am seeing along the edges of my eyeglass lenses?

I am near-sighted. Here is the phenomenon: I stand in front of a light source that is situated on the ceiling so that it reflects off my eyeglass lenses and appears circular. It is a white light ...
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1answer
27 views

Formula for blurring out a grid of holes

Place a camera lens with focal length f_l mm and camera sensor size w mm and h mm behind an ...
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1answer
25 views

Reflection and Transmission at oblique incidence Griffiths

I’m working through Griffiths E&M and on page 408 he gives the boundary conditions for oblique incidence. I’ve spent an hour trying to understand how he goes from the boundary condition $$\...
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1answer
44 views

Images created by a pair of perpendicular mirrors

Let's assume we're given a pair of perpendicular mirrors. Let us set a system of coordinates as shown on the picture - the position of an object is given by $(x_p, y_p)$. Of course we would observe ...
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1answer
48 views

What is the frequency of white light? [duplicate]

We can see white LED light after a combination of red, green & blue LED together. Then what is the frequency of white light? Whether it lies between 380 Hz - 700 Hz? There has to be a frequency ...
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1answer
55 views

In Young double slit experiment, if whole of the space between the slits and the screen is filled with some optical medium (excluding air and vacuum)

Then a slab is introduced in front of one of the slits. What will be the path difference offered by the slab? The equation must be, according to my school teacher: $$\left({n/n'-1}\right)p=d\sin\...
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How to find distance given candela values on a coordinate system?

Consider this diagram: Let's say that some lamp at 1.5D, 2R has a luminous intensity of 35,000 cd. I want to find the maximum distance at which this lamp can put 5 lux on the road. I understand ...
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44 views

Need an IR transmitting plastic that is white in color and partially opaque to visible light?

I need an IR transmitting plastic material (85% or better) that is white in color, but partially opaque to visible light. Does anyone know of such a substance?
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2answers
43 views

Gaussian Beam propogation in a fiber

If we suppose that a Gaussian beam traveles in the fiber with diagonal end as it shown in the image, so I have several questions: 1- Do we get in the end of the fiber Evanescent field (Total ...
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1answer
9 views

Spectrograph difference between cross disperses and echelle gratings?

In echelle spectrographs, the presence of echelle gratings and cross-dispersers is common. What task does each one perform? Why are the cross-dispersers needed?
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Red and blue sideband transitions in ions and two level system approximation

Suppose we have a trapped ion (approximated as 2 level system) of mass $m$ and transition frequency $\omega_{10}$ in a harmonic confinement with frequencies $\omega_x, \omega_y, \omega_z$ such that ...
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1answer
20 views

Scattered fields in surface plasmon excitation with grating

We need to use prism-coupling (e.g. Kretschmann or Otto configuration) or use grating to excite surface plasmon between metal and dielectric. What I understand is that when we use a grating or ...
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1answer
33 views

Effect of IR absorption on visible region refractive index of Glass

If we go with the Lorentz oscillator model of susceptibility, it is obvious that high frequency resonance tails raise the refractive index of low frequency light. However, I recently came across a ...
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1answer
47 views

Unitary Transformation of an Interfering Beam Splitter

I was reading this research paper Quantum interference enables constant time quantum information processing and was confused by one particular expression involving the Hamiltonian of a beam splitter. ...
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14 views

Can scintillator crystals be used for solid state lasers?

For example, a theoretical design would involve a yellow Cerium-YAG scintillator crystal which emits yellow light when stimulated by ultraviolet radiation. Has this approach ever been tried and if so ...
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2answers
66 views

Snell's law and Fermat's principle

I have read this sentence on a book about the Snell's law of refraction, referring on a ray that passes from air ($n_1=1$) to glass ($n_2=1.55$): "Snell's equation can be derived from Fermat's ...
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4answers
144 views

Is there 100% pure white? [duplicate]

Is it possible to have an object 100% pure white without sky blue or sun color tinting the pure whiteness of the photons reflecting/deflecting off an object? Are there any lights that can produce pure ...
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34 views

Looking for an EM or QM mechanistic explanation for Rayleigh scattering

The common quick answer I usually see on the internet for questions like 'why is the sky blue' is that shorter wavelength light is scattered to a greater extant than longer wavelengths. The ...
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What is the critical volume/mass of non-deuterated water that appears blue to our eyes?

A glass of water appears clear, but a swimming pool appears blue. At some point there must be a switch and I am wondering if anyone knows what that point is (or if its so gradual we can't tell). Does ...